Abstract:

A millimeter waveband switch which enables high isolation without
increasing passing loss, includes a first switching element that is
connected in series between input and output terminals through which a
signal passes; and a first transmission line having an electrical length
of 1/2 wavelength and which is connected in parallel with the first
switching element. Alternatively, the millimeter waveband switch may
include: a first switching element having a first end connected in
parallel to input and output terminals through which a signal passes; a
first transmission line having an electrical length of 1/2 wavelength
which is connected in parallel with the first switching element; and a
second transmission line having an electrical length of 1/2 wavelength
and which is connected between ground and a second end of the first
switching element.

Claims:

1. A millimeter waveband switch, comprising:a first switching element that
is connected in series between input and output terminals through which a
signal passes; anda first transmission line having an length of 1/2
wavelength and which is connected in parallel with the first switching
element.

2. The millimeter waveband switch according to claim 1, further comprising
a second switching element that is connected between ground and a point
of an electrical length of 1/4 wavelength of the electrical length of 1/2
wavelength of the first transmission line.

3. A millimeter waveband switch, comprising:a first switching element
having a first end connected in parallel to input and output terminals
through which a signal passes;a first transmission line having an
electrical length of 1/2 wavelength and which is connected in parallel
with the first switching element; anda second transmission line having an
electrical length of 1/4 wavelength and which is connected between ground
and an second end of the first switching element.

4. A millimeter waveband switch, comprising n (wherein n is an integer and
at least 2) of the millimeter waveband switches according to claim 1
connected to constitute an n-branch changeover switch.

5. The millimeter waveband switch according to claim 1, wherein the
switching element comprises one of field effect transistor and a diode.

6. A millimeter waveband switch, comprising n (wherein n is an integer and
at least 2) of the millimeter waveband switches according to claim 2
connected to constitute an n-branch changeover switch.

7. A millimeter waveband switch, comprising n (wherein n is an integer and
at least 2) of the millimeter waveband switches according to claim 3
connected to constitute an n-branch changeover switch.

8. The millimeter waveband switch according to claim 2, wherein the
switching element comprises one of a field effect transistor and a diode.

9. The millimeter waveband switch according to claim 3, wherein the
switching element comprises one of a field effect transistor and a diode.

10. The millimeter waveband switch according to claim 4, wherein the
switching element comprises one of a field effect transistor and a diode.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a switch that mainly operates on a
millimeter waveband.

[0003]2. Description of the Related Art

[0004]FIGS. 29 and 30 are diagrams showing the general circuit structures
of the conventional millimeter waveband switch. In the figures, T denotes
a field effect transistor (FET) which is used as a switching element, P1
and P2 are input and output terminals, L1 is a transmission line, V1 is a
control voltage supply terminal, and D is a diode.

[0005]The switch that operates on the millimeter waveband is generally
structured in such a manner that the FET or the diode is arranged in
parallel to the transmission line (corresponding to L1 in the figures)
through which a signal passes for the purpose of reducing loss when the
switch is on.

[0006]In the conventional structures, for example, in the case of the
structure shown in FIG. 29, the isolation characteristic when the switch
is off depends on the on-resistance (Ron) value of the switching element
which is arranged in parallel to the transmission line. FIGS. 31 and 32
are diagrams showing the circuit structures of the conventional
millimeter waveband switch that aims at high isolation. As shown in FIGS.
31 and 32, it is required that two or more switching elements are
arranged in parallel in order to aim at the high isolation.

[0007]Also, as the structure of the switch for obtaining the high
isolation when the switch is off, there is a structure in which
inductance that resonates with an off capacitance when the switch is off
at a desired frequency is arranged in series (for example, refer to JP
11-284203 A). FIG. 33 is a diagram showing the circuit structure of the
conventional millimeter waveband switch in which the inductance is
arranged in series with the switch in order to aim at the high isolation.

[0008]However, the conventional art suffers from the following problem.

[0009]In the conventional switch having the above circuit structure, the
isolation characteristic is improved. However, there arises such a
problem that the passing loss increases due to the on-resistance of the
switching element when the switch is on.

SUMMARY OF THE INVENTION

[0010]The present invention has been made to solve the above problem, and
therefore has an object to provide a millimeter waveband switch, which
enables high isolation without increasing passing loss.

[0011]A millimeter waveband switch according to the present invention
includes: a first switching element that is connected in series between
input and output terminals through which a signal passes; and a first
transmission line having an electric length of 1/2 wavelength which is
connected in parallel to the first switching element.

[0012]Moreover, a millimeter waveband switch according to the present
invention includes: a first switching element having one end connected in
parallel between input and output terminals through which a signal
passes; a first transmission line having an electric length of 1/2
wavelength which is connected in parallel to the first switching element;
and a second transmission line having an electric length of 1/4
wavelength which is connected between a ground and another end of a
parallel circuit including the first switching element and the first
transmission line.

[0013]According to the present invention, the parallel circuit including
the transmission line having an electric length of 1/2 wavelength and the
switching element is connected in parallel or in series between the input
and output terminals through which a signal passes, thereby making it
possible to obtain the millimeter waveband switch which enables the high
isolation without an increase in passing loss.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]In the accompanying drawings:

[0015]FIG. 1 is a diagram showing a first circuit structure of a
millimeter waveband switch according to a first embodiment of the present
invention;

[0016]FIG. 2 shows an equivalent circuit of the millimeter waveband switch
shown in FIG. 1 when the switch is on in the first embodiment of the
present invention;

[0017]FIG. 3 shows an equivalent circuit of the millimeter waveband switch
shown in FIG. 1 when the switch is off in the first embodiment of the
present invention;

[0018]FIG. 4 shows an example of a frequency characteristic showing
calculation results of isolation when the millimeter waveband switch
shown in FIG. 1 according to the first embodiment of the present
invention is off;

[0019]FIG. 5 shows an example of a frequency characteristic showing
calculation results of passing loss when the millimeter waveband switch
shown in FIG. 1 according to the first embodiment of the present
invention is on;

[0020]FIG. 6 is a diagram showing a second circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0021]FIG. 7 shows an equivalent circuit of the millimeter waveband switch
shown in FIG. 6 when the switch is off in the first embodiment of the
present invention;

[0022]FIG. 8 shows an equivalent circuit of the millimeter waveband switch
shown in FIG. 6 when the switch is on in the first embodiment of the
present invention;

[0023]FIG. 9 shows an example of a frequency characteristic showing
calculation results of isolation when the millimeter waveband switch
shown in FIG. 6 according to the first embodiment of the present
invention is off;

[0024]FIG. 10 shows an example of a frequency characteristic showing
calculation results of passing loss when the millimeter waveband switch
shown in FIG. 6 according to the first embodiment of the present
invention is on;

[0025]FIG. 11 is a diagram showing a third circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0026]FIG. 12 is a diagram showing a fourth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0027]FIG. 13 is a diagram showing a fifth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0028]FIG. 14 is a diagram showing a sixth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0029]FIG. 15 is a diagram showing a seventh circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0030]FIG. 16 is a diagram showing an eighth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0031]FIG. 17 is a diagram showing a ninth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0032]FIG. 18 is a diagram showing a tenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0033]FIG. 19 is a diagram showing an eleventh circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0034]FIG. 20 is a diagram showing a twelfth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0035]FIG. 21 is a diagram showing a thirteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0036]FIG. 22 shows an example of a frequency characteristic showing
calculation results of isolation when the millimeter waveband switch
shown in FIG. 21 according to the first embodiment of the present
invention is off;

[0037]FIG. 23 shows an example of a frequency characteristic showing
calculation results of passing loss when the millimeter waveband switch
shown in FIG. 21 according to the first embodiment of the present
invention is on;

[0038]FIG. 24 is a diagram showing a fourteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0039]FIG. 25 is a diagram showing a fifteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0040]FIG. 26 is a diagram showing a sixteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0041]FIG. 27 is a diagram showing a seventeenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0042]FIG. 28 is a diagram showing an eighteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention;

[0043]FIG. 29 is a diagram showing a general circuit structure of a
conventional millimeter waveband switch;

[0044]FIG. 30 is a diagram showing a general circuit structure of another
conventional millimeter waveband switch;

[0045]FIG. 31 is a diagram showing a circuit structure of a conventional
millimeter waveband switch that aims at high isolation;

[0046]FIG. 32 is a diagram showing a circuit structure of another
conventional millimeter waveband switch that aims at high isolation; and

[0047]FIG. 33 is a diagram showing a circuit structure of a conventional
millimeter waveband switch in which inductance is arranged in series in
order to aim at high isolation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0048]Now, a description is given of a preferred embodiment of a
millimeter waveband switch according to the present invention with
reference to the drawings.

First Embodiment

[0049]FIG. 1 is a diagram showing a first circuit structure of a
millimeter waveband switch according to a first embodiment of the present
invention. A transmission line having an electric length of 1/2
wavelength of a millimeter waveband signal passing therethrough is
arranged at both ends of a switching element which is arranged in series
between input and output terminals (P1 and P2 in the figure). In FIG. 1,
L denotes a transmission line of 1/2 wavelength long, T denotes an FET
that operates as the switching element, V1 denotes a control voltage
supply terminal, and R denotes a voltage supply resistor.

[0050]Hereinafter, a description is given of the operation of the
millimeter waveband switch shown in FIG. 1 according to the first
embodiment. FIG. 2 shows an equivalent circuit of the millimeter waveband
switch shown in FIG. 1 when the switch is on in the first embodiment of
the present invention. Also, FIG. 3 shows an equivalent circuit of the
millimeter waveband switch shown in FIG. 1 when the switch is off in the
first embodiment of the present invention.

[0051]When a voltage of Vc<Vp (pinch off voltage of the FET) is applied
to the control voltage supply terminal, the FET has a capacitance (Coff)
indicated by Coff as shown in FIG. 2, and an impedance Zt of the FET can
be represented by the following Expression (1).

Zt=1/-jωoff (1)

[0052]In the case of selecting the FET having a gate width which is small
in the off capacitance, the impedance (Zt of FIG. 2) of the FET becomes
large on the millimeter waveband which is higher in the frequency, and
the millimeter waveband signal passes through the 1/2 wavelength line.

[0053]On the other hand, in the case where a voltage of Vc=0 V is applied
to the control voltage supply terminal of the FET when the switch is off,
the FET can be regarded substantially as a resistor (Ron of FIG. 3), and
the impedance (Zt of FIG. 3) of the FET is represented by the following
Expression (2).

Zt=Ron (2)

[0054]In this case, the signals of the millimeter waveband which have been
input from P1 are separated into signals that pass through the resistor
of Ron and are partially attenuated and signals that pass through the 1/2
wavelength line and are delayed in phase by 180 degrees. Those signals
are combined together at a point A of FIG. 3. Accordingly, because both
of those signals operate so as to cancel each other, the high isolation
can be realized.

[0055]FIG. 4 shows an example of a frequency characteristic showing
calculation results of the isolation when the millimeter waveband switch
shown in FIG. 1 according to the first embodiment of the present
invention is off. In FIG. 4, S1_off represents the calculation results of
the isolation when the millimeter waveband switch shown in FIG. 1
according to the first embodiment is off (FIG. 3). Also, S2_off
represents the calculation results of the isolation when the conventional
millimeter waveband switch shown in FIG. 29 is off. With the use of the
circuit structure according to the first embodiment, there is obtained
the effect of improving the isolation on 77 GHz band.

[0056]FIG. 5 shows an example of a frequency characteristic showing
calculation results of the passing loss when the millimeter waveband
switch shown in FIG. 1 according to the first embodiment of the present
invention is on. In FIG. 5, S1_on represents the calculation results of
the passing loss when the millimeter waveband switch shown in FIG. 1
according to the first embodiment is on (FIG. 2). Also, S2_on represents
the calculation results of the passing loss when the conventional
millimeter waveband switch shown in FIG. 29 is on. With the use of the
circuit structure according to the first embodiment, there is obtained
the effect of increasing no passing loss on 77 GHz band.

[0057]In fact, it is necessary to take the parasitic component of the FET
into consideration on the millimeter waveband. For that reason, the
length of the 1/2 wavelength line is required to adjust a slight increase
or decrease on a desired frequency band. Similarly, in this case, the
same advantage is obtained. Further, as the FET, GaAs-FET, GaN-FET, or
HBT can be used.

[0058]FIG. 6 is a diagram showing a second circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. In the 1/2 wavelength line of the first circuit
structure diagram shown in FIG. 1, the FET (T2 of FIG. 6) is used as the
second switching element at a point of the 1/4 wavelength. FIG. 7 shows
an equivalent circuit of the millimeter waveband switch shown in FIG. 6
when the switch is off in the first embodiment of the present invention.
FIG. 8 shows an equivalent circuit of the millimeter waveband switch
shown in FIG. 6 when the switch is on in the first embodiment of the
present invention.

[0059]When the switch is off (FIG. 7), the amplitude of the signal whose
phase is delayed by 180 degrees is attenuated by the second FET (T2) and
combined together, thereby enabling the isolation to be improved more
than the above circuit structure shown in FIG. 1. The gate width of the
second FET is selected to have substantially the same degree as the
amount of attenuation caused by the first FET.

[0060]FIG. 9 shows an example of a frequency characteristic showing
calculation results of the isolation when the millimeter waveband switch
shown in FIG. 6 according to the first embodiment of the present
invention is off. In FIG. 9, S1_off represents the calculation results of
the isolation when the millimeter waveband switch shown in FIG. 1
according to the first embodiment is off (FIG. 3). Also, S3_off
represents the calculation results of the isolation when the millimeter
waveband switch shown in FIG. 6 according to the first embodiment is off
(FIG. 7).

[0061]Also, FIG. 10 shows an example of a frequency characteristic showing
calculation results of the passing loss when the millimeter waveband
switch shown in FIG. 6 according to the first embodiment of the present
invention is on. In FIG. 10, S1_on represents the calculation results of
the passing loss when the millimeter waveband switch shown in FIG. 1
according to the first embodiment is on (FIG. 2). Also, S3_on represents
the calculation results of the passing loss when the millimeter waveband
switch shown in FIG. 6 according to the first embodiment is on (FIG. 8).

[0062]As shown in FIGS. 9 and 10, it is found that the isolation
characteristic (S3_off of FIG. 9) when the millimeter waveband switch
having the second circuit structure is off is increased in isolation more
than the isolation characteristic (S1_off of FIG. 9) when the millimeter
waveband switch having the first circuit structure is off. Also, it is
found that the passing characteristic when the switch is on hardly
varies.

[0063]FIG. 11 is a diagram showing a third circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 11 shows a structural example of a two-branch
switch using the first circuit structure shown in FIG. 1. In FIG. 11, L3
represents a transmission line having a length of 1/4 wavelength which is
connected to a branch point. With the use of the first circuit structure
shown in FIG. 1, it is possible to obtain the high isolation when the
switch is off without increasing the passing loss when the switch is on
even in the two-branch switch.

[0064]FIG. 12 is a diagram showing a fourth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 12 shows a structural example of an n-branch
switch using the first circuit structure shown in FIG. 1. Similarly, it
is possible to obtain the high isolation when the switch is off without
increasing the passing loss when the switch is on even in the n-branch
switch.

[0065]FIG. 13 is a diagram showing a fifth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 13 shows a structural example using a diode as
the switching element in the first circuit structure shown in FIG. 1.
With the use of the diode, both of the off capacitance (Coff) when the
switch is off and the on-resistance (Ron) when the switch is on can be
reduced more than those in the first circuit structure using the FET. As
a result, the switching characteristic is obtained with lower passing
loss and higher isolation.

[0066]FIG. 14 is a diagram showing a sixth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 14 shows a structural example of a two-branch
switch using the fifth circuit structure shown in FIG. 13. With the use
of the fifth circuit structure shown in FIG. 13, it is possible to obtain
the high isolation when the switch is off without increasing the passing
loss when the switch is on even in the two-branch switch.

[0067]FIG. 15 is a diagram showing a seventh circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 15 shows a structural example of an n-branch
switch using the fifth circuit structure shown in FIG. 13. Similarly,
with the use of the fifth circuit structure shown in FIG. 13, it is
possible to obtain the high isolation when the switch is off without
increasing the passing loss when the switch is on even in the n-branch
switch.

[0068]FIG. 16 is a diagram showing an eighth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 16 shows a structural example of a two-branch
switch using the second circuit structure shown in FIG. 6. In FIG. 16, L3
represents a transmission line which is connected to a branch point. With
the use of the second circuit structure shown in FIG. 6, it is possible
to obtain the high isolation when the switch is off without increasing
the passing loss when the switch is on even in the two-branch switch.

[0069]FIG. 17 is a diagram showing a ninth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 17 shows a structural example of an n-branch
switch using the second circuit structure shown in FIG. 6. In FIG. 17, L3
represents a transmission line which is connected to a branch point. With
the use of the second circuit structure shown in FIG. 6, likewise, it is
possible to obtain the high isolation when the switch is off without
increasing the passing loss when the switch is on even in the n-branch
switch.

[0070]FIG. 18 is a diagram showing a tenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 18 shows a structural example using a diode as
the switching element in the second circuit structure shown in FIG. 6.
With the use of the diode, both of the off capacitance (Coff) when the
switch is off and the on-resistance (Ron) when the switch is on can be
reduced more than those in the second circuit structure using the FET. As
a result, the switching characteristic is obtained with lower passing
loss and higher isolation.

[0071]FIG. 19 is a diagram showing an eleventh circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 19 shows a structural example of a two-branch
switch using the tenth circuit structure shown in FIG. 18. With the use
of the tenth circuit structure shown in FIG. 18, it is possible to obtain
the high isolation when the switch is off without increasing the passing
loss when the switch is on even in the two-branch switch.

[0072]FIG. 20 is a diagram showing a twelfth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 20 shows a structural example of an n-branch
switch using the tenth circuit structure shown in FIG. 18. With the use
of the tenth circuit structure shown in FIG. 18, it is possible to obtain
the high isolation when the switch is off without increasing the passing
loss when the switch is on even in the n-branch switch.

[0073]FIG. 21 is a diagram showing a thirteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 21 shows a modified example of the first circuit
structure shown in FIG. 1. In FIG. 21, L represents a transmission line
having a length of 1/2 wavelength, and L2 represents a transmission line
having a length of 1/4 wavelength. Hereinafter, a description is given of
the operation of the millimeter waveband switch having the thirteenth
circuit structure.

[0074]When Vc=0 V is applied to the control voltage supply terminal V1,
the FET becomes the on-resistance (Ron) as with the millimeter waveband
switch having the first circuit structure shown in FIG. 1. As a result,
the impedance at a point S of FIG. 21 becomes small, and the signal that
has been input to the input terminal P1 is blocked off.

[0075]Also, when a voltage of Vc<Vp is applied to the control voltage
supply terminal V1, the FET becomes the off capacitance (Coff) as with
the millimeter waveband switch having the first circuit structure shown
in FIG. 1. As a result, the impedance at the point S of FIG. 21 becomes
large, and the signal that has been input to the input terminal P1 passes
to the output terminal P2.

[0076]FIG. 22 shows an example of a frequency characteristic showing
calculation results of the isolation when the millimeter waveband switch
shown in FIG. 21 according to the first embodiment of the present
invention is off. In FIG. 22, S4_off represents the calculation results
of the isolation when the millimeter waveband switch shown in FIG. 21
according to the first embodiment is off. Also, S2_off represents the
calculation results of the isolation when the conventional millimeter
waveband switch shown in FIG. 29 is off.

[0077]Also, FIG. 23 shows an example of a frequency characteristic showing
calculation results of the passing loss when the millimeter waveband
switch shown in FIG. 21 according to the first embodiment of the present
invention is on. In FIG. 23, S4_on represents the calculation results of
the passing loss when the millimeter waveband switch shown in FIG. 21
according to the first embodiment is on. Also, S2_on represents the
calculation results of the passing loss when the conventional millimeter
waveband switch shown in FIG. 29 is on.

[0078]Similarly, with the use of the thirteenth circuit structure shown in
FIG. 21, the isolation (S4_off of FIG. 22) when the switch is off
increases more than that of the conventional example, and the passing
loss (S4_on of FIG. 23) when the switch is on can obtain substantially
the same performance as that of the conventional example.

[0079]FIG. 24 is a diagram showing a fourteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 24 shows a structural example of a two-branch
switch using the thirteenth circuit structure shown in FIG. 21. With the
use of the thirteenth circuit structure shown in FIG. 21, it is possible
to obtain the high isolation when the switch is off without increasing
the passing loss when the switch is on even in the two-branch switch.

[0080]FIG. 25 is a diagram showing a fifteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 25 shows a structural example of an n-branch
switch using the thirteenth circuit structure shown in FIG. 21. Likewise,
it is possible to obtain the high isolation when the switch is off
without increasing the passing loss when the switch is on even in the
n-branch switch.

[0081]FIG. 26 is a diagram showing a sixteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 26 shows a structural example using a diode as
the switching element in the thirteenth circuit structure shown in FIG.
21. With the use of the diode as the switching element, likewise, the
switching characteristic can be obtained with lower passing loss and
higher isolation.

[0082]FIG. 27 is a diagram showing a seventeenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 27 shows a structural example of a two-branch
switch using the sixteenth circuit structure shown in FIG. 26. With the
use of the sixteenth circuit structure shown in FIG. 26, it is possible
to obtain the high isolation when the switch is off without increasing
the passing loss when the switch is on even in the two-branch switch.

[0083]FIG. 28 is a diagram showing an eighteenth circuit structure of the
millimeter waveband switch according to the first embodiment of the
present invention. FIG. 28 shows a structural example of an n-branch
switch using the sixteenth circuit structure shown in FIG. 26. With the
use of the sixteenth circuit structure shown in FIG. 26, it is similarly
possible to obtain the high isolation when the switch is off without
increasing the passing loss when the switch is on even in the n-branch
switch.

[0084]As has been described above, according to the first embodiment, the
parallel circuit including the transmission line having the electric
length of 1/2 wavelength and the switching element is connected in
parallel or in series between the input and output terminals through
which the signal passes, thereby making it possible to obtain the
millimeter waveband switch that enables the high isolation without
increasing the passing loss.